Thinning hair in women: causes, red flags and when to get it checked

Each hair follicle cycles through growth, rest and shedding. In pattern hair loss the growth phase shortens and follicles miniaturise under the influence of genes and hormones. In telogen effluvium a trigger pushes many hairs into the shedding phase simultaneously, causing a sudden increase in shedding.

• Female pattern hair loss (androgenetic alopecia): gradual thinning at the crown and widening parting, with a family history.

• Telogen effluvium: diffuse shedding after illness, fever, surgery, childbirth, crash dieting or emotional stress.

• Iron deficiency and low ferritin, particularly with heavy periods or vegetarian diets.

• Thyroid disease (underactive or overactive).

• Polycystic ovary syndrome and other hormonal imbalances, menopause.

• Medicines: some contraceptives, anticoagulants, retinoids, beta blockers, antidepressants and chemotherapy.

• Traction from tight hairstyles, extensions and chemical or heat damage.

• Alopecia areata, scarring alopecias, scalp infections and nutritional problems, which are less common.

Patchy bald areas, a red, scaly, painful or scarred scalp, rapid loss, eyebrow or body hair loss, hair loss with facial hair growth, irregular periods, acne or voice change (androgen excess), symptoms of thyroid disease, and significant weight loss or fatigue warrant assessment.

• GP within days to weeks: sudden severe shedding, a painful or scarred patch on the scalp.

• GP within weeks: thinning with irregular periods, excess facial hair, fatigue or weight change.

• Dermatology: patchy loss or suspected scarring alopecia.

• Routine: gradual thinning over months to years, for assessment and treatment options.

The doctor asks about the pattern and timeline, family history, diet, recent illness, childbirth, medicines, hair styling, periods, menopause, thyroid symptoms and stress. They examine the scalp, parting width, hair density and pull test, and look for signs of androgen excess.

• Blood tests: full blood count, ferritin, thyroid function, vitamin D, B12 and folate.

• Hormone tests (testosterone, SHBG, prolactin and others) if there are signs of PCOS or androgen excess.

• Dermoscopy and trichoscopy: examine hair shaft and follicle patterns.

• Scalp biopsy: for suspected scarring alopecia or unclear diagnoses.

• Fungal scrapings: if scalp infection is suspected.

Eat a balanced diet with enough protein and iron, treat any deficiency found, avoid tight hairstyles and excess heat or chemical treatments, and handle hair gently. Topical minoxidil is licensed for female pattern hair loss and needs months of consistent use. Other prescription options are considered by specialists, and camouflage, wigs and fibres offer practical support. Be wary of unproven supplements.

The NHS route is a GP and dermatology referral for complex cases. Private dermatology, trichology and treatments such as PRP are available, with variable evidence.